Kyasanur Forest Disease Virus

Authored by: Pradeep B.J. Reddy , Ambuj Srivastava , Priyabrata Pattnaik

Manual of Security Sensitive Microbes and Toxins

Print publication date:  April  2014
Online publication date:  April  2014

Print ISBN: 9781466553965
eBook ISBN: 9781466553989
Adobe ISBN:


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Kyasanur forest disease (KFD), also called as monkey fever, is an infectious hemorrhagic disease caused by a highly pathogenic virus, namely, Kyasanur forest disease virus (KFDV). 1 KFDV falls under the genus Flavivirus within the family Flaviviridae. There are about 70 identified viruses in the Flaviviridae family 2 and most of them are arthropod-borne, which are transmitted to vertebrates by either infected mosquitoes or ticks. 3 Dengue virus, yellow fever virus, and Japanese encephalitis virus are the few important flaviviruses transmitted by mosquitoes, whereas KFDV, Omsk hemorrhagic fever virus (OHFV), and Alkhurma virus (ALKV) are the few viruses transmitted by ticks in this genus. 4 Generally these tick-borne encephalitis viruses (TBEV) are defined geographically with KFD being restricted to the Indian subcontinent. KFD is a febrile illness and it was initially identified in the Shimoga district of the Karnataka state in 1957 (Figure 13.1). 1,5 Initially, the symptoms were similar to that of typhoid fever when the outbreak occurred; however, the negative results in Widal test ruled out the possibility. 1 With numerous fatal cases in the black-faced langur and the red-faced bonnet monkeys occurring parallelly, it was suspected to be the dawn of yellow fever virus infection in India. 1 Later, the causative virus was isolated from the postmortem blood and visceral organs of dead langurs and bonnet monkeys, and the same virus was also isolated from the Haemaphysalis ticks. 1 The disease was named KFD and the causative agent KFDV after the name of the forest where it was identified for the first time. KFD epidemics have occurred every year in this region with an average of about 400–500 cases annually, reflecting the prevalence of active foci of infection in the forest region. The highest recorded incidence was in 1983, with 1555 cases and 150 deaths. 6 KFD has so far been localized largely to the Karnataka state, although it was found occasionally in some other parts of India. KFDV commonly infects monkeys, that is, black-faced langur (Presbytis entellus) and red-faced bonnet monkeys (Macaca radiata), and KFDV gets transmitted by the bite of infective ticks (Haemaphysalis spinigera), especially at its nymphal stage, and the ticks remain infectious throughout their life. 7 KFDV also circulates in small animals such as rodents, shrews, and birds. 79 KFDV-transmitting adult ticks (H. spinigera) commonly feed on the large animals, and neutralizing antibodies have been found in large animals like cattle, buffaloes, goats, and wild bears and also in a number of avian species, but hardly have they suffered from KFD (Table 13.1). 10 Direct transmission of the virus from rodents to humans has been documented; however, person-to-person transmission has not been known yet. During 1994, a variant of KFD was isolated from a butcher living in the Mecca province of Saudi Arabia, which was named as Alkhurma virus (ALKV). 11 Due to the strong genetic similarity between KFDV and ALKV, the latter was considered to be a subtype of KFDV introduced into Saudi Arabia. 12

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